For example, exercise and perusing a goal very ambitiously are both types of stress, except they ultimately benefit the body. Areas of the brain, including the hippocampus, amygdala and prefrontal cortex can pick up on positive stressful experiences and cause “stress-induced structural remodeling” of the brain, which means you experience alterations in behavioral and physiological responses to these positive events. The result is that in the future you’re better able to handle similar situations because you learn from them, associate them with a reward and stop perceiving them as threatening.
You are already far beyond the need for using an entrainment product as a meditation aid. Those who sincerely believe this to be the case would not have come searching for a meditation site such as Project Meditation to help them learn and practice meditation and brainwave entrainment. They would probably not even bother with using an entrainment aid; hence this entire discussion would be irrelevant to them. The fact that you are here, reading this, seeking to benefit from incorporating meditation and brainwave entrainment to aid in your existing meditation practice suggests you are not one of these folks whose development is so advanced that entrainment is of no use to you.

Theta brainwaves in the frequency range of 6 to 9 hertz are known as thalpha waves because of their proximity to alpha waves. They are seen during states of high suggestibility, during hypnosis, and during paranormal experience and are also connected to an increase in human growth hormone (HGH) levels and higher blood flow to the brain. Theta brainwaves sit between the realms of the subconscious and conscious mind, making them an especially useful brainwave state for developing creative thinking, working through emotional problems, and integrating subconscious and conscious experience. 
They are not beyond what is “normal” but for most of us they are outside of what is “typical”. Whether we consciously seek them or not, somewhere in the back of our minds we hold beliefs that because meditation and brainwave entrainment are beyond our usual set of experiences, then the evidence that they are having some sort of effect on us must also be outside of our normal range of experiences.
Entrainment is a term originally derived from complex systems theory, and denotes the way that two or more independent, autonomous oscillators with differing rhythms or frequencies, when situated in a context and at a proximity where they can interact for long enough, influence each other mutually, to a degree dependent on coupling force, such that they adjust until both oscillate with the same frequency. Examples include the mechanical entrainment or cyclic synchronization of two electric clothes dryers placed in close proximity, and the biological entrainment evident in the synchronized illumination of fireflies.[13]